ref: 063c3f398e949895bb9795539e83a2e0be364376
dir: /man/2/crypt-0intro/
.TH CRYPT-INTRO 2 .SH NAME Crypt intro \- introduction to the .B Crypt cryptography module .SH SYNOPSIS .EX include "ipints.m"; ipints := load IPints IPints->PATH; IPint: import ipints; include "crypt.m"; crypt := load Crypt Crypt->PATH; .EE .SH DESCRIPTION .B Crypt contains a mixed set of functions that variously: .IP \(bu form cryptographically secure digests; see .IR crypt-sha1 (2) .IP \(bu generate public/private key pairs; see .IR crypt-gensk (2) .IP \(bu encrypt data, using AES, DES, or IDEA; see .IR crypt-crypt (2) .IP \(bu create and verify cryptographic signatures using the public keys; see .IR crypt-sign (2) .SS "Public Key Cryptography" Public key cryptography has many uses. Inferno relies on it only for digital signatures. The private key may be used to digitally sign data, the public one to verify the signature. .PP Inferno provides three data types to represent the different components of the public key signature scheme. The .B PK adt contains the data necessary to construct a public key; the .B SK adt contains the data necessary to construct a secret key. A key contains the public or secret parameters for the signature algorithm specified by the adt's pick tag. Ownership of a key is not recorded in the key value itself but in a separate certificate. Finally, the .B PKsig adt contains one or more values representing a given form of digital signature. .PP Certificates and indeed signature representations are varied, and implemented by other modules. .SS "Large Precision Arithmetic" Many .B Crypt operations require integers much larger than .B int or .BR big . It therefore uses the multiple-precision package .IR ipints (2). That module's .B IPint adt stands for infinite precision integer, though, for space considerations, our implementation limits the maximum integer to 2\u\s-2\&8192\s0\d-1. .PP An .B IPint can be converted into two external formats. The first is an array of bytes in which the first byte is the highest order byte of the integer. This format is useful when communicating with the .IR ssl (3) device. The second is similar but represents the array of bytes as text, using either base 16 or a MIME base 64 format, allowing .BR IPint s to be stored in files or transmitted across networks in a human readable form. .SH SOURCE .br .B /libinterp/crypt.c .br .B /libinterp/ipint.c .br .B /libmp .br .B /libsec .SH SEE ALSO .IR security-intro (2) .br B. Schneier, .IR "Applied Cryptography" , 1996, J. Wiley & Sons, Inc.